New naphtoquinones derivatives from the edible bulbs of Eleutherine americana and their protective effect on the injury of human umbilical vein endothelial cells

Phenolic constituents with antibacterial activity from Eleutherine bulbosa

Eleutherine bulbosa (Mill.) Urb. is a medicinal and edible plant with various benefits for humans and animals. In this work, four new phenolic constituents (1-4), along with six known phenolic compounds (5-10) were obtained from the red bulbs of E. bulbosa. Their structures with absolute configurations were characterized by extensive spectroscopic analysis, combined with HR-ESI-MS and quantum mechanical electronic circular dichroism (ECD). Compounds 1 and 2 are novel homologous and heterodimers, respectively, featuring an unusual spiro ring system. All isolated phenolic constituents were tested for their antibacterial effects. The results revealed four phenolic compounds 1-3 and 7 showed moderate antibacterial activity against Bacillus subtilis, Staphylococcus aureus and Escherichia coli with minimum inhibitory concentration (MIC) values ranging from 15.6 to 250.0 μg/mL.

Quinones: Biosynthesis, Characterization of 13 C Spectroscopical Data and Pharmacological Activities

Quinones are natural products widely distributed in nature, which are involved in stages of several vital biological processes, with mostly having a variety of pharmacological properties. The main groups comprising most of these compounds are benzoquinones, naphthoquinones, anthraquinones, and phenanthraquinones. Quinone isolation has been a focus of study around the world in recent years; for this reason, this study approaches the junction of natural quinones identified by 13 C Nuclear Magnetic Resonance (NMR) spectroscopic analytical techniques. The methodology used to obtain the data collected articles from various databases on quinones from 2000 to 2022. As a result, 137 compounds were selected, among which 70 were characterized for the first time in the period investigated; moreover, the study also discusses the biosynthetic pathways of quinones and the pharmacological activities of the compounds found, giving an overview of the various applications of these compounds.

Natural epoxyquinoids: isolation, biological activity and synthesis. An update

Epoxyquinoids are of continuing interest due to their wide natural distribution and diverse biological activities, including, but not limited to, antibacterial, antifungal, anticancer, enzyme inhibitory, and others. The last review on their total synthesis was published in 2017. Since then, almost 100 articles have been published on their isolation from nature and their biological profile. In addition, the review specifically considers synthesis, including total and enantioselective, as well as the development of shorter approaches for the construction of epoxyquinoids with complex chemical architecture. Thus, this review focuses on progress in this area in order to stimulate further research.

Dimeric (Poly)Hydroxynaphthazarins, Metabolites of Echinoderms and Lichens: The History of the Synthesis and Structure Elucidation

This review provides information on the synthesis and revision of the structures of natural dimeric (poly)hydroxynaphthazarins, metabolites of echinoderms and lichens, and on the refinement of the direction and mechanism of reactions in the synthesis of some of these compounds.

Development of a UPLC-MS/MS Method for Pharmacokinetic and Tissue Distribution of Isoeleutherin, Eleutherin, and Eleutherol in Bulbus eleutherinis in Rats

Bulbus eleutherinis is a classical traditional Dai medicine, and has been widely used in clinical treatment of coronary heart disease (CHD) in Yunnan, China. Naphthoquinone, as the main active compound in Bulbus eleutherinis in treating CHD, mainly contain isoeleutherin, eleutherin, and eleutherol. This study aimed to investigate the in vivo parameters of isoeleutherin, eleutherin, and eleutherol. In this work, male Sprague Dawley (SD) rats were treated with the three compounds by oral administration, and then blood and tissue samples were collected. A novel UPLC-MS/MS (ultra-performance liquid chromatography-tandem mass spectrometry) method has been developed to determine the absolute oral bioavailability, and the tissue distribution profile of the compounds. Acetonitrile and 0.1% (v/v) solution of formic acid were selected as the mobile phase of the chromatogram. C18 column was employed. Betamethasone was used as an internal standard in the method. The detection was performed with a multireaction monitor of scan type in positive ion mode by MS/MS. Our data showed linearity of the method with r over 0.9983. Lower limits of quantification of isoeleutherin, eleutherin, and eleutherol were 1.00, 3.84, and 0.498 ng/mL, respectively. The overall precision of the compounds was less than 12.68%, recoveries ranged from 85.44 to 103.83%, and the accuracy of the compounds in plasma was between 91.56 and 110.75%. The stability assay showed that they were stable (87.83–114.62%) under different conditions in plasma. For oral administration, the half-lives of isoeleutherin, eleutherin, and eleutherol was 6.11, 7.30, and 3.07 hours, respectively. The absolute oral bioavailabilities were 5.38, 4.64, and 2.47%, respectively. Moreover, the three components had the highest distribution in small intestine. In conclusion, the established method was successfully applied to the determination of the in vivo parameters of the three components in SD rats. This work provides a reference for the development of new drugs of Bulbus eleutherinis in the future.

Naphthoquinone Derivatives Isolated from Plants: Recent Advances in Biological Activity

Naturally occurring naphthoquinones (NQs) comprising highly reactive small molecules are the subject of increasing attention due to their promising biological activities such as antioxidant, antimicrobial, apoptosis-inducing activities, and especially anticancer activity. Lapachol, lapachone, and napabucasin belong to the NQs and are in phase II clinical trials for the treatment of many cancers. This review aims to provide a comprehensive and updated overview on the biological activities of several new NQs isolated from different species of plants reported from January 2013 to January 2020, their potential therapeutic applications and their clinical significance.

Eleucanainones A and B: Two Dimeric Structures from the Bulbs of Eleutherine americana with Anti-MRSA Activity

Two naphthoquinone-derived heterodimers with unprecedented carbon skeletons, eleucanainones A (1) and B (2), were isolated from the bulbs of Eleutherine americana. Their structures were elucidated by comprehensive spectroscopic methods. The structures of 1 and 2 were determined to be the first examples of dibenzofuran- and naphthalenone-containing naphthoquinone dimers. Compound 1 exhibited significant anti-MRSA activity in vitro with minimum inhibitory concentration (MIC) values of 0.78 μg/mL by downregulation of basal expression of agrA, cidA, icaA and sarA in methicillin-resistant S. aureus (MRSA).